How to have unique random number?

Question

This is how i am generating a unique no in between 1 to 6 and getting appropriate images from the drawable folder.

Random rand = new Random();
// n = the n         


        

Answer 1

For your particular use-case, this should do the trick.

Random rand = new Random();
// n = the number of images
List imgNames = new ArrayList(n);
for (int i = 0; i < n; i++) { 
    imgNames.add("card" + (i + 1)) 
}
while (!imageNames.isEmpty()) {
    String imgName = imgNames.remove(rand.next(imageNames.size());
    int id = getResources().getIdentifier(imgName, "drawable", getPackageName());
    imgView.setImageResource(id);
}

Beware that this does not scale well as n gets large. The remove operation is O(n) for an ArrayList or a LinkedList. But for n in the hundreds or thousands, this is probably insignificant compared with loading and displaying the images.

Also, as the comments noted "unique random numbers" is a contradiction in terms. What you are after is a random permutation of the set of numbers from 1 to n. My solution gives you this without an explicit "shuffling" step, and that's sufficient for your use-case.